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Spotted: First quadruple star image produced by gravity

By Liz Kruesi

SEEING quadruple? For the first time, astronomers have seen an image of a single supernova split into four by a gravitational lens. The splintered stellar explosion may help calibrate distances across the universe.

Gravitational lenses are the result of massive celestial objects, like stars, galaxies or even dark matter, bending light as it passes near them. Sometimes gravitational lenses produce multiple images of a single object behind them. The effect is similar to looking at a candle through the base of a wine glass.

A supernova whose light has been bent in several directions can tell us the speed of the universe

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Despite decades of searching, no such stellar explosions had turned up. But now, Patrick Kelly at the University of California, Berkeley, and his colleagues say they’ve found one.

The supernova appeared in images of the galaxy cluster MACS J1149.6+2223 taken on 10 November by the Hubble Space Telescope. Four bright sources surrounding one of the cluster’s giant galaxies all appear to be related to the same object, a smaller galaxy located behind the cluster, meaning they are probably all images of the same star. The object didn’t appear in earlier pictures of the same galaxy cluster, so the team think it is the bright, fatal explosion of a supernova (arxiv.org/abs/1411.6009).

“This is a fantastic discovery,” says Robert Quimby at the University of Tokyo in Japan. “The authors make a good case that this is a supernova seen through a gravitational lens.”

This article appeared in print under the headline “Once, twice, three, four times a supernova…”